1. Field of the Invention
The present invention relates generally to rotors and electrical machines using rotors, and, more particularly, but not by way of limitation, to line-start permanent-magnet (LSPM) rotors, rotor components, and machines comprising LSPM rotors.
2. Description of Related Art
Rotors and machines using rotors have been known in the art for some time. Electrical machines such as motors traditionally include brushes and a rotor with wire windings. Such traditional winding-based rotors are relatively inefficient compared with PM rotors, and PM rotors may generally be made smaller than traditional winding-based rotors for a given capacity or output. As a result, machines using PM rotors may generally be made smaller than those with traditional winding-based rotors. PM rotors generally use permanent magnet material instead of traditional electrical wire windings, such that a PM rotor machine does not require reactive current from a power supply. As such, power consumption of PM machines can generally be reduced relative to those using traditional winding-based rotors for a given output. For example, some PM rotor machines can achieve a higher power factor, higher power density, and higher efficiency (e.g., 25% to 120% of the rated load) relative to a traditional winding-based machine. Maintenance costs of PM machines may also be reduced, as the simpler configuration (e.g., without windings, brushes, etc.) may result in fewer parts or points of potential failure. Some embodiments of PM machines are known as line-start permanent-magnet (LSPM) machines, and may include what is known as a “squirrel cage” with a plurality of bars around the LSPM rotor core.